Pancreatic cystic neoplasm: the role of cyst morphology, cyst fluid analysis, and expectant management.

Background: Among pancreatic cysts, mucinous cystadenoma, and intraductal papillary mucinous neoplasms have the potential for malignant transformation. Differentiation between benign and potentially malignant/malignant (PMM) cysts remains difficult. The purpose of this study was to: (1) identify the diagnostic value of endoscopic ultrasound findings, serum, and cyst fluid tumor markers (CA19-9 and CEA), (2) determine the rate of subsequent surgical resection in patients initially managed conservatively, and (3) determine the role of cyst fluid viscosity "string sign" in differentiating pancreatic cysts.
Methods: Patients with cytologic or pathologic diagnosis for pancreatic cystic neoplasms were analyzed.
Results: The study included 79 patients. Cyst fluid CEA had a median of 1.0 ng/mL in benign cysts and 471.1 ng/mL in PMM cysts (P < .0001). Cyst fluid CA 19-9 was not statistically significant (P = .22). Neither serum CA 19-9 nor CEA was useful (P = .68 and P = .31). Increased cyst fluid viscosity was associated with PMM cysts (P < .0001). Median string sign was 0 mm in benign cysts and 3.5 mm in PMM cysts. The presence of thick walls (5 of 5, 100%) or intracystic growth (6 of 6, 100%) were associated with PMM cysts. Of the 50 patients with PMM cysts, 19 were treated conservatively. In those patients followed for more than 6 months, 2 of 12 (16.7%) had surgical resection after a median of 29.5 months for worrisome changes on imaging.
Conclusions: The presence of a thick cyst wall or intracystic growth, elevated cyst fluid CEA, and a long "string sign" were associated with PMM cysts. 16.7% of patients with a PMM cyst managed conservatively ultimately required surgical resection.